Semiconductor integrated circuit apparatus which is capable of controlling a substrate voltage under the low source voltage driving of a miniaturized mosfet

ABSTRACT

Provided is a semiconductor integrated circuit apparatus capable of controlling the substrate voltage of a MOSFET so that the drain current for an arbitrary gate voltage value in a subthreshold region or a saturated region will be free from temperature dependence and process variation dependence, thereby enhancing the stable operation thereof. The semiconductor integrated circuit apparatus includes: an integrated circuit main body having a plurality of MOSFETs on a semiconductor substrate; a monitor unit for monitoring at least one of the drain currents of the plurality of MOSFETs; and a substrate voltage regulating unit for controlling the substrate voltage of the semiconductor substrate so as to keep constant the drain current. The monitor unit includes a constant current source and a monitoring MOSFET formed on the same substrate as the plurality of MOSFETs, the substrate voltage regulating unit includes a comparison unit for comparing the source potential of the monitoring MOSFET with a predetermined reference potential with the drain terminal of the monitoring MOSFET and the drain terminals of the plurality of MOSFETs connected to ground, and the substrate voltage regulating unit feeds back the output voltage output based on the comparison result by the comparison unit to the substrate voltage of the monitoring MOSFET.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor integrated circuitapparatus, and in particular to semiconductor integrated circuitapparatus which is capable of controlling a substrate voltage under thelow source voltage driving of a miniaturized MOSFET.

2. Description of the Related Art

In recent years, with the advancement of a miniaturization processconcerning the fabrication of semiconductor integrated circuitapparatus, the channel length of a MOSFET has come to be fabricated onthe order of 0.1 μm or lower. With such process miniaturization, a lowvoltage of 1 V or less has come to be used as a source voltage and thefollowing reports have been made.

It is reported that, in the environment of a source voltage of 1 V orless, the threshold value and the voltage value of MOSFET are not scaledand the operation speed of a CMOS circuit is inverted in state of lowtemperatures and high temperatures (refer to Kouichi Kanda and threeothers, “Design Impact of Positive Temperature Dependence on DrainCurrent in Sub-1V CMOS VLSIs”, October 2001, IEEE Journal of Solid-StateCircuits, vol. 36, No. 10, p. 1559-1564).

It is reported that, for an SRAM as an example of semiconductorintegrated circuit apparatus, miniaturization lowers the noise marginthus impairing the stabilized read/write operation from/to the memorycell (refer to Takakuni Douseki and one other Static-Noise MarginAnalysis for a Scaled-Down CMOS Memory Cell, Journal of IEICE vol.J75-C-2 No. 7, pp. 350-361, July 1992. (In Japanese)).

As a technique to lower the minimum operating voltage under the lowsource voltage, there is a method for controlling a balance between thesource-drain currents of p-type and n-type MOSFETs by way of a substratebias (refer to Goichi Ono and one other, “Threshold-voltage balance forMinimum Supply Operation”, 2002 IEEE, 2002 Symposium on VLSI CircuitDigest of Technical Papers).

In the aforementioned method (described in Goichi Ono and one other,“Threshold-voltage balance for Minimum Supply Operation”), the delay ofan predetermined critical path and a clock cycle is compared, thesubstrate bias of p-type and n-type MOSFETs is controlled, and the inputand output of an inverter comprising a p-type MOSFET and an n-typeMOSFET is shorted. With this method, the voltage value of the inverteris compared with the arbitrarily set voltage value of a voltage monitorand correction to offset process variations in the MOSFET so as tostabilize operation with a predetermined voltage.

However, the related art technologies as disclosed in Goichi Ono and oneother, “Threshold-voltage balance for Minimum Supply Operation”, 2002IEEE, 2002 Symposium on VLSI Circuit Digest of Technical Papers do notconsider the fact that, in the environment of a source voltage of 1 V orless, the operation speed of a CMOS circuit is inverted at lowtemperatures and high temperatures described in Kouichi Kanda and threeothers, “Design Impact of Positive Temperature Dependence on DrainCurrent in Sub-1V CMOS VLSIs”, October 2001, IEEE Journal of Solid-StateCircuits, vol. 36, No. 10, p. 1559-1564 and thus cannot control thesubstrate voltage of MOSFET to avoid temperature dependence.

The related art low voltage technology (refer to FIG. 9 P/N Vt matchingscheme in Goichi Ono and one other, “Threshold-voltage balance forMinimum Supply Operation”, 2002 IEEE, 2002 Symposium on VLSI CircuitDigest of Technical Papers) regulates the Ids of an n-type MOSFET basedon a p-type MOSFET, so that it cannot set a subthreshold leakage currentor a saturation current to an optimum value.

In other words, according to this method, in semiconductor integratedcircuit apparatus incorporating a large-scale memory, stability ofoperation cannot be enhanced in case the leakage current in the memoryreaches several tens to several hundreds of that in other logiccircuits.

Or, the method cannot assure the characteristics of the output range ofan analog operational amplifier. In circuits such as a dynamic circuitand a domino amplifier as a ore-charged amplifier often used in thetiming borrow system, the noise margin is determined by the thresholdvalue of the MOSFET so that it is impossible to supply an optimumthreshold value to stabilize the circuit operation.

Assume a configuration where another “scheme” to perform substratecontrol of a p-type MOSFET is implemented on top of an n-type MOSFET inthe same system as Goichi Ono and one other, “Threshold-voltage balancefor Minimum Supply Operation”, 2002 IEEE, 2002 Symposium on VLSI CircuitDigest of Technical Papers (see FIG. 9). Assume that semiconductorintegrated circuit apparatus whose Ids of the p-type MOSFET is high andthe Ids of the n-type MOSFET is low has been fabricate due to processvariations.

In this case, the Ids of the p-type MOSFET is high so that the Ids ofthe n-type MOSFET is low in Goichi Ono and one other, “Threshold-voltagebalance for Minimum Supply Operation”, 2002 IEEE, 2002 Symposium on VLSICircuit Digest of Technical Papers (see FIG. 9). The Ids of the n-typeMOSFET is low so that substrate control of the p-type MOSFET is made todecrease the Ids of the p-type MOSFET.

Use of the above system produces a MOSFET having the characteristicsopposite to the process variations. In other words, the Ids of thep-type MOSFET is controlled low and the Ids of the n-type MOSFET iscontrolled high. In this way, even when there are separate circuitswhich are based on n-type and p-type MOSFETs, it is impossible tooptimize the Ids of the p-type and n-type MOSFETs.

The technology of Goichi Ono and one other, “Threshold-voltage balancefor Minimum Supply Operation”, 2002 IEEE, 2002 Symposium on VLSI CircuitDigest of Technical Papers (see FIG. 11, SA-Vt CMOS system) is a controlmethod dependent on the delay in a predetermined critical path. Thismakes it necessary to physically arrange a dummy path circuitcorresponding to the predetermined critical path, which increases thearea of the semiconductor integrated circuit apparatus.

The technology of the aforesaid non-patent document 3 provides themethod for controlling a substrate bias of MOSFET using the delay in thecritical path. With such a method, however, in MOSFET devices differentin substrate bias dependence within the critical path, such e.g. asdevices different in gate oxide thickness or devices different in gateoxide film dielectric constant, in order to match circuit delays witheach other, a different substrate voltage cannot be applied to eachdevice different in substrate bias dependence.

In case a large number of critical paths are present under each of theprocess conditions, temperature conditions and voltage conditions in thesemiconductor integrated circuit apparatus and the corresponding logicgenerator circuits differ from each other, it is necessary to physicallyarrange a large number of dummy path circuits corresponding to the largenumber of critical paths, which further increases the area of thesemiconductor integrated circuit apparatus.

When a large substrate voltage is applied, the transistorcharacteristics show the opposite of the regular behavior. On theforward bias side, an excessive forward voltage applied shows bipolarcharacteristics thus allowing a forward current to flow between thesubstrate and the drain. The drain-source current is amplified by thesubstrate voltage. This invalidates the current control across the drainand the source by a gate current.

On the back bias side, an excessive back bias applied generates a GIDL(Gate-Induced Drain Leakage) effect which is an increase in thesubthreshold current. In this way, applying an excessive substrate biasinverts the transistor characteristics, causing deadlock to be applied,not feedback.

The bipolar effect is described for example in Tzuen-His Huang et al.,“Base Current Reversal Phenomenon in a CMOS Compatible High Gain n-p-ngated Bipolar Transistor”, February 1995, IEEE TRANSACTIONS ON ELECTRONDEVICES, VOL. 42, NO. 2, P321. The GIDL effect is described for examplein Hiroyuki Mizuno and seven others, “An 18-μ A Standby Current 1.8-V,200 MHz Microprocessor with Self-Substrate-Biased Data-Retention Mode”,NOVEMBER 1999, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 34, No. 11, p.1392-1500.

SUMMARY OF THE INVENTION

The invention has been accomplished in view of the aforementionedcircumstances and aims at providing semiconductor integrated circuitapparatus capable of controlling the substrate voltage of a MOSFET sothat the drain current of the MOSFET, in particular the drain currentfor an arbitrary gate voltage value in a subthreshold region or asaturated region will be free from temperature dependence and processvariation dependence, thereby enhancing the stable operation.

In order to attain the object, the first aspect of the invention issemiconductor integrated circuit apparatus characterized by comprising:an integrated circuit main body including a plurality of MOSFETs on asemiconductor substrate; monitor means for monitoring at least one ofthe drain currents of the plurality of MOSFETs; and substrate voltageregulating means for controlling the substrate voltage of thesemiconductor substrate so as to keep constant the drain current.

With this configuration, the monitor means monitors the drain current ofthe MOSFETs, and in accordance with the monitored current value, thesubstrate voltage regulating means regulates the substrate voltage toregulate the drain voltage of the plurality of MOSFETs in the integratedcircuit main body. This regulation reduces the temperature dependence ofa drain current in case there occurred a variation in the temperature ofthe semiconductor integrated circuit apparatus and reduces variations inthe characteristics of the semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence). Thisenhances the stable operation of the semiconductor integrated circuitapparatus.

The second aspect of the invention is semiconductor integrated circuitapparatus characterized by comprising a plurality of the substratevoltage regulating means.

With this configuration, when circuits and devices having differentcharacteristics are present within the semiconductor integrated circuit,or the like, the plurality of substrate voltage regulating means can beregulated to a substrate voltage suitable for the individual circuitsand devices.

The third aspect of the invention is semiconductor integrated circuitapparatus characterized by having first substrate voltage regulatingmeans for regulating a substrate potential so that the individualthreshold values of the plurality of MOSFETs become uniform, and secondsubstrate voltage regulating means for regulating a substrate potentialso that the individual drain currents of the plurality of MOSFETs areconstant, and in that the first substrate voltage current regulatingmeans is used for substrate voltage regulation of a portion of thesemiconductor integrated circuit main body in which portion a noisemargin is lower than a predetermined value, and that the secondsubstrate voltage current regulating means is used for substrate voltageregulation of a portion of the semiconductor integrated circuit mainbody in which portion a noise margin is higher than the predeterminedvalue.

With this configuration, it is possible to realize stable circuitoperation and furthermore to prevent reversion of temperature dependenceof delay time under a low voltage. Thus, it is possible to reduce aleakage current under high temperature. Besides, it is possible toincrease circuit speed and furthermore to prevent reversion oftemperature dependence of delay time under a low voltage. Thus, it ispossible to reduce a leakage current under high temperature.

The fourth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the interior of the integrated circuitmain body is divided into a plurality of regions, and substrate voltageregulating means for regulating the substrate voltage of a MOSFET withinthe region is connected to the inside or vicinity of each of theregions.

With this configuration, it is possible to apply to each region asubstrate voltage for obtaining an appropriate threshold value andsaturation current when the device characteristics of MOSFETs within thesemiconductor integrated circuit have local dependence. Thus, it ispossible to reduce variations in circuit characteristics within thesemiconductor integrated circuit.

The fifth aspect of the invention is semiconductor integrated circuitapparatus characterized in that MOSFETs different in devicecharacteristics for a substrate voltage are mounted together within theintegrated circuit main body, and the same substrate voltage regulatingmeans is connected to MOSFET groups substantially identical in thedevice characteristics to each other.

With this configuration, it is possible to apply an appropriatesubstrate voltage, without deteriorating a circuit noise margin, to eachof MOSFET groups different in device characteristics for a substratevoltage.

The sixth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the drain current is a drain current foran arbitrary gate voltage value in a subthreshold region or a saturatedregion.

With this configuration, it is possible to regulate to an optimum valuethe drain current in the subthreshold region or saturated region of aplurality of MOSFETs in the integrated circuit main body by monitoring,on monitoring means, the drain current for an arbitrary gate voltagevalue in the subthreshold region or saturated region of the MOSFETs.

This regulation reduces the temperature dependence of a drain current incase there occurred a variation in the temperature of semiconductorintegrated circuit apparatus and reduces variations in thecharacteristics of the individual semiconductor integrated circuitapparatus created by fabrication process (process variation dependence).This enhances the stable operation of the semiconductor integratedcircuit apparatus.

The seventh aspect of the invention is semiconductor integrated circuitapparatus characterized in that the gin of the transistor is keptconstant by the substrate voltage regulating means.

With this configuration, it is possible to provide a circuit generatinggm in the neighborhood of a predetermined voltage value thus keepingconstant the gm of the transistor so that the temperature dependence andprocess variation dependence of the semiconductor integrated circuitapparatus will be eliminated.

The eighth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the monitor means comprises a constantcurrent source and a monitoring MOSFET formed on the same substrate asthe plurality of MOSFETs, that the substrate voltage regulating meanscomprises comparison means for comparing the source potential of themonitoring MOSFET with a predetermined reference potential with thedrain terminal of the monitoring MOSFET and the drain terminals of theplurality of MOSFETs connected to the ground potential, and that thesubstrate voltage regulating means feeds back the output voltage outputbased on the comparison result by the comparison means to the substratevoltage of the monitoring MOSFET.

With this configuration, the monitor means comprising a constant currentsource and a monitoring MOSFET monitors the drain current of the MOSFET.The substrate voltage regulating means compares the source potential ofthe monitoring MOSFET determined in accordance with the monitoredcurrent value with a predetermined reference potential by way ofcomparison means and outputs the output voltage according to thecomparison result, and feeds back the output voltage to the substratevoltage of the monitoring MOSFET, thereby keeping constant the thresholdvalue (Vth) or drain current (Ids) of each of the plurality of MOSFETsarranged on the integrated circuit main body. In this way, the thresholdvalue (Vth) or drain current (Ids) of each of the MOSFETs is keptconstant so that the drain current of the plurality of MOSFETs on theintegrated circuit main body is regulated to an optimum value.

This regulation reduces the temperature dependence of a drain current incase there occurred a variation in the temperature of the semiconductorintegrated circuit apparatus and reduces variations in thecharacteristics of the semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence).

The ninth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the reference potential is a supplypotential to the integrated circuit main body.

With this configuration, it is possible to keep constant the thresholdvalue (Vth) or drain current (Ids) of each of the plurality of MOSFETsarranged on the integrated circuit main body, by comparing, oncomparison means, the source potential or ground potential as a supplypotential to the integrated circuit main body with the source potentialof the monitoring MOSFET and outputting the output voltage according tothe comparison result, and feeding back the output voltage to thesubstrate voltage of the monitoring MOSFET. In this way, the thresholdvalue (Vth) or drain current (Ids) of each of the MOSFETs is keptconstant so that the drain current of the plurality of MOSFETs on theintegrated circuit main body is regulated to an optimum value.

This regulation reduces the temperature dependence of a drain current incase there occurred a variation in the temperature of the semiconductorintegrated circuit apparatus and reduces variations in thecharacteristics of individual semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence).

The tenth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the substrate voltage regulating meansoutputs a voltage value obtained by providing by way of limiting means,the upper and lower limits of the output voltage output based on thecomparison result of the comparison means.

With this configuration, the output which is based on the comparisonresult of the comparison means is limited within a predetermined valuerange by way of the limiting means. Thus it is possible to provide theupper and lower limits of the substrate voltage output from thesubstrate voltage regulating means, thereby preventing a so-called“deadlock”, a phenomenon where an appropriate feedback is not applied tothe substrate voltage of the monitoring MOSFET thus stabilizing thesubstrate voltage regulating means in an abnormal state.

The eleventh aspect of the invention is semiconductor integrated circuitapparatus characterized in that the monitoring MOSFET is a p-typemonitoring MOSFET, that the upper limit of the output voltage value ofthe substrate voltage regulating means is set to a voltage equal to orabove the supply potential of the integrated circuit main body andwithin a range where the GIDL effect does not occur in the p-typemonitoring MOSFET, and that the lower limit of the output voltage valueof the substrate voltage regulating means is set to a voltage below thesupply potential of the integrated circuit main body and within a rangewhere the p-type monitoring MOSFET does not show the bipolarcharacteristics.

With this configuration, it is possible to prevent the GIDL effect wherethe transistor characteristics are opposite to the regularcharacteristics as well as the bipolar characteristics where a forwardcurrent flows between the substrate and the drain thus reducing thedrain-source current, in case a large amount of substrate voltage isapplied.

The twelfth aspect of the invention is semiconductor integrated circuitapparatus characterized in that the monitoring MOSFET is an n-typemonitoring MOSFET, that the upper limit of the output voltage value ofthe substrate voltage regulating means is set to a voltage equal to orabove the ground potential of the integrated circuit main body andwithin a range where the n-type monitoring MOSFET does not show thebipolar characteristics, and that the lower limit of the output voltagevalue of the substrate voltage regulating means is set to a voltagebelow the ground potential of the integrated circuit main body andwithin a range where the GIDL effect does not occur in the n-typemonitoring MOSFET.

With this configuration, it is possible to prevent the GIDL effect wherethe transistor characteristics are opposite to the regularcharacteristics as well as the bipolar characteristics where a forwardcurrent flows between the substrate and the drain thus reducing thedrain-source current, in case a large amount of substrate voltage isapplied.

The thirteenth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the output of the limiting meansis connected to voltage supply means for supplying a source voltage tothe integrated circuit main body, and by being configured such that thesource voltage is raised when a substrate voltage is an upper limitvoltage or more and the source voltage is lowered when the substratevoltage is a lower limit voltage or less.

With this configuration, the source voltage supplied to the integratedcircuit main body can be made variable. Thus, it is possible to furthersecure the improvement in the threshold value characteristics,saturation current characteristics, and gm characteristics of MOSFET bythe substrate voltage regulating means.

The fourteenth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the constant current source hasa leakage current canceling MOSFET substantially identical in transistorsize to the monitoring MOSFET, that when the leakage current cancelingMOSFET is an n-type MOSFET, a source-drain current provided when thegate and drain of the n-type MOSFET have substantially the samepotential is added, and that when the leakage current canceling MOSFETis a p-type MOSFET, a source-drain current provided when the gate anddrain of the p-type MOSFET have substantially the same potential isadded.

With this configuration, the leakage component of a parasitic bipolar orGIDL effect can be cancelled. Thus, it is possible to apply a substratevoltage capable of securing the original threshold value and saturationcurrent of the MOSFET of the monitor means.

The fifteenth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that a well region that provides thesubstrate of the leakage current canceling MOSFET is separated from awell region that provides the substrate of the monitoring MOSFET.

With this configuration, it is possible to eliminate the leakage currentcomponent caused by the parasitic bipolar effect between the MOSFET ofthe monitor means and the leakage current canceling MOSFET. Thus, it ispossible to apply a substrate voltage capable of securing the originalthreshold value and saturation current of the MOSFET of the monitormeans.

The sixteenth aspect of the invention is semiconductor integratedcircuit apparatus characterized by having substrate voltage regulatingmeans for regulating a substrate potential so that the individualthreshold values of the plurality of MOSFETs become uniform, and in thata voltage is applied to the gate of the monitoring MOSFET as the voltagevalue is changed in accordance with temperature so as to provide a moregradual gradient than the temperature gradient of the threshold valuesformed when a voltage applied to the gate is set to be constant.

With this configuration, the gain of the integrated circuit main bodydue to a reduction in junction capacity of MOSFET can be made lower thanwhen the gate voltage of the monitoring MOSFET of the substrate voltageregulating means is constant. Besides, variations in threshold value ofindividual MOSFETs within the integrated circuit main body can besuppressed even when the temperature is changed.

The seventeenth aspect of the invention is semiconductor integratedcircuit apparatus characterized by having frequency-voltage conversionmeans, and by being configured such that a signal originating from aclock supplied to the integrated circuit main body is inputted to thefrequency-voltage conversion means, that the frequency of the signal isconverted into a voltage by the frequency-voltage conversion means, andthat the voltage is applied to the gate of a MOSFET constituting themonitor means.

With this configuration, the threshold value regulated by a circuitgenerating a constant threshold value (Vth) can be set to be higher atthe time of a clock low frequency than at the time of a high frequencyfor the integrated circuit main body. Thus, MOSFET device leakage isreduced during the use at a low frequency.

The eighteenth aspect of the invention is semiconductor integratedcircuit apparatus, having a n-well region, which become a substrate of ap-type MOSFET, and a p-well region, which is provided inside said n-wellregion, and become a substrate of a n-type MOSFET, characterized in thatthere are provided a second p-well region and a second n-well region,and that the second p-well region is electrically connected to thesubstrate potential of the n-type MOSFET and the second n-well region iselectrically connected to the ground potential of the n-type MOSFET.

With this configuration, voltage variation between the source andsubstrate of the n-type MOSFET is reduced, thus enabling high-precisionapplication of a substrate voltage. The nineteenth aspect of theinvention is semiconductor integrated circuit apparatus, characterizedby that a source and substrate are independently controlled, wherein agate capacity of MOSFET is added between the source of the MOSFET andthe substrate of the MOSFET.

With this configuration, voltage variation between the source andsubstrate of the n-type MOSFET is reduced, thus enabling high-precisionapplication of a substrate voltage.

The twentieth aspect of the invention is semiconductor integratedcircuit apparatus, having a n-well region, which become a substrate of ap-type MOSFET, and a p-well region, which is provided inside said n-wellregion, and become a substrate of a n-type MOSFET, characterized in thatan electric capacity value between a p-well region that provides thesubstrate of an n-type MOSFET and the ground potential of the n-typeMOSFET is higher than an electric capacity value between the p-wellregion and an n-well region that provides the substrate of a p-typeMOSFET.

With this configuration, voltage variation between the source andsubstrate of the n-type MOSFET is reduced, thus enablinghigher-precision application of a substrate voltage.

The twenty-first aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a feedback buffer and that the substrate voltage of the MOSFETof the feedback buffer is set by the substrate voltage regulating means.

With this configuration, stable operation of the semiconductorintegrated circuit apparatus is allowed even when the feedback buffer isdriven on a low voltage. Moreover, the leakage current is reduced.

The twenty-second aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a memory circuit and that the substrate voltage of the MOSFETof the memory circuit is set by the substrate voltage regulating means.

With this configuration, it is possible to control the source-substratevoltage value of the MOSFET in the memory circuit so that the draincurrent for an arbitrary gate voltage value in a subthreshold regionwill be free from temperature dependence and process variationdependence, thereby preventing corruption of memory data by asubthreshold leakage.

The twenty-third aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises an SRAM and that the substrate voltage of the MOSFET of theSRAM is set by the substrate voltage regulating means.

With this configuration, it is possible to reduce the temperaturedependence of the noise margin at low voltages. This allows operation ofthe semiconductor integrated circuit apparatus at a low voltage therebyreducing the power consumption of the SRAM.

The twenty-fourth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a circuit of the timing borrow system and that the substratevoltage of the MOSFET of the circuit of the timing borrow system is setby the substrate voltage regulating means.

With this configuration, it is possible to reduce the temperaturedependence and process variation dependence of a circuit of the timingborrow system, since the static noise margin of the circuit of thetiming borrow system is determined by the threshold value of the MOSFET.It is also possible to reduce the leakage current in the circuit of thetiming borrow system.

The twenty-fifth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a differential operational amplifier and that the substratevoltage of the MOSFET of the differential operational amplifier is setby the substrate voltage regulating means.

With this configuration, it is possible to reduce the temperaturedependence and process variation dependence of the lower limit voltagein the output range of the differential operational amplifier.

The twenty-sixth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a voltage-controlled oscillator and that the substrate voltageof the MOSFET of the voltage-controlled oscillator is set by thesubstrate voltage regulating means.

With this configuration, it is possible to reduce the temperaturedependence and process variation dependence of the frequency responsewith respect to the input voltage of the voltage-controlled oscillator.

The twenty-seventh aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a CMOS logic circuit and that the substrate voltage of theMOSFET of the CMOS logic circuit is set by the substrate voltageregulating means.

With this configuration, it is possible to reduce the temperaturedependence and process variation dependence of a delay in the CMOS logiccircuit.

The twenty-eighth aspect of the invention is semiconductor integratedcircuit apparatus characterized in that the integrated circuit main bodycomprises a current-controlled oscillator and that the substrate voltageof the MOSFET of the current-controlled oscillator is set by thesubstrate voltage regulating means.

With this configuration, it is possible to keep constant the delay valueof the current-controlled oscillator and reduce the temperaturedependence and process variation dependence of the oscillatingfrequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing semiconductor integrated circuitapparatus according to the first embodiment of the invention;

FIG. 2 is a circuit diagram showing an example of the comparator section(CMOS side) comprising a limiter;

FIG. 3 shows the Ids-Vgs characteristics used to explain the GIDLeffect;

FIG. 4 shows the simulation values of the drain current Ids obtainedwhen the substrate voltage Vbs of the p-type MOSFET used to explain thebipolar characteristics is varied;

FIG. 5 is a circuit diagram showing semiconductor integrated circuitapparatus according to the second embodiment of the invention;

FIG. 6 is a circuit diagram showing an example of the comparator section(NMOS side) comprising a limiter;

FIG. 7 shows the simulation values of the drain current Ids obtainedwhen the substrate voltage Vbs of the p-type MOSFET used to explain thebipolar characteristics is varied;

FIG. 8 is a circuit diagram showing semiconductor integrated circuitapparatus according to the third embodiment of the invention;

FIG. 9 is a circuit diagram showing semiconductor integrated circuitapparatus according to the fourth embodiment of the invention;

FIG. 10 is a circuit diagram showing semiconductor integrated circuitapparatus according to the fifth embodiment of the invention;

FIG. 11 is a graph showing the circuit simulation result of a staticnoise margin width with respect to the source voltage in thesemiconductor integrated circuit apparatus according to the fifthembodiment of the invention;

FIG. 12 is a graph showing the circuit simulation result of thetemperature dependence of a leakage current in the semiconductorintegrated circuit apparatus according to the fifth embodiment of theinvention;

FIG. 13 is a circuit diagram showing semiconductor integrated circuitapparatus according to the sixth embodiment of the invention;

FIG. 14 is a circuit diagram showing semiconductor integrated circuitapparatus according to the seventh embodiment of the invention;

FIG. 15 is a graph showing the simulation result of the read noisemargin of SRAM in the semiconductor integrated circuit apparatusaccording to the seventh embodiment of the invention;

FIG. 16 is a graph showing the simulation result of the write noisemargin of SRAM in the semiconductor integrated circuit apparatusaccording to the seventh embodiment of the invention;

FIG. 17 is a circuit diagram showing semiconductor integrated circuitapparatus according to the eighth embodiment of the invention;

FIG. 18 is a circuit diagram showing semiconductor integrated circuitapparatus according to the ninth embodiment of the invention;

FIG. 19 is a circuit diagram showing semiconductor integrated circuitapparatus according to the tenth embodiment of the invention;

FIG. 20 is a circuit diagram showing semiconductor integrated circuitapparatus according to the eleventh embodiment of the invention;

FIG. 21 is a circuit diagram showing semiconductor integrated circuitapparatus according to the twelfth embodiment of the invention; and

FIG. 22 is a circuit diagram showing semiconductor integrated circuitapparatus according to the thirteenth embodiment of the invention.

FIG. 23 is a configuration example in which the characteristics of aconstant current source 12B have been further approximated to idealcurrent source characteristics;

FIG. 24 is a diagram showing a p-well region that provides the substrateof an n-type MOSFET shown in FIG. 23;

FIG. 25 is a configuration example in which the characteristics of aconstant current source 12A shown in FIG. 1 have been furtherapproximated to ideal current source characteristics;

FIG. 26 is a circuit diagram showing a multi-port register file that isan example of semiconductor integrated circuit apparatus according tothe fourteenth embodiment of the invention;

FIG. 27 is temperature characteristics of a relative value of delay timefor a data read (Normalized Delay) in the multi-port register filehaving the configuration of FIG. 26;

FIG. 28 is temperature characteristics of a relative value of currentconsumption during operation (Normalized Current) in the multi-portregister file having the configuration of FIG. 26;

FIG. 29 is a schematic diagram showing an example in which thesemiconductor integrated circuit apparatus according to the fourteenthembodiment of the invention is applied to an SRAM circuit;

FIG. 30 is a diagram showing in schematic form the circuit layout of anintegrated circuit main body according to the fifteenth embodiment ofthe invention;

FIG. 31 is a diagram showing in schematic form the configuration of thesixteenth embodiment of the invention;

FIG. 32 is a block diagram showing the seventeenth embodiment of theinvention;

FIG. 33 is a graph showing the frequency-voltage conversioncharacteristics of a frequency-voltage conversion circuit of FIG. 32;

FIG. 34 is a schematic diagram A showing the characteristics of theeighteenth embodiment of the invention; a diagram B showing thevariation of BN and variation of Vss produced when a capacity componentCC is absent; a diagram C showing the variation of BP and variation ofVss produced when the capacity component CC is present;

FIG. 35 is a schematic diagram showing an example of a configuration forrealizing the eighteenth embodiment of the invention;

FIG. 36 is a schematic diagram showing an example in which the capacitycomponent of FIG. 34 comprises a gate capacity;

FIG. 37 is a graph showing an effect of the nineteenth embodiment of theinvention; and

FIG. 38 is a circuit diagram showing an example of the configuration ofthe twentieth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described referring to thedrawings.

First Embodiment

FIG. 1 is a circuit diagram showing semiconductor integrated circuitapparatus 10A according to the first embodiment. As shown in FIG. 1, thesemiconductor integrated circuit apparatus 10A comprises a circuit 14Agenerating a constant threshold value (Vth) (substrate voltageregulating means) including monitor means 15A including a p-type MOSFET11A and a constant current source 12A and a comparator section 13A(comparison means), and an integrated circuit main body 16A.

In the first embodiment, the threshold value Vth of the MOSFET is Vgs(gate-source voltage) obtained for example in case Ids=50 nA×(W/L) whenVDD=1 V. The Ids is a source-drain current of MOSFET, W is the channelwidth of MOSFET, and L is the channel length of MOSFET.

The p-type MOSFET 11A is arranged on the same substrate as theintegrated circuit main body 16A. In this embodiment, the transistorsize of the p-type MOSFET 11A is: channel width W=1.2 μm, channel lengthL=0.12 μm.

The constant current source 12A and the comparator section 13A may be ormay not be arranged on the same substrate as the integrated circuit mainbody 16A.

The constant current source 12A uses a material which is “nottemperature dependent” and is composed of for example a band gapreference circuit showing the constant current characteristics. The term“not temperature dependent” is defined equal to or below 20 PPM/° C.(which does not mean “temperature independent”). The constant currentsource 12A supplies a current of 500 nA.

The comparator section 13A comprises for example an operationalamplifier and an OTA. At least a reference voltage value and a measuredvoltage value are input to the input terminal of the comparator section13A. The reference voltage value and the measured voltage value arecompared with each other. In case the measured voltage value is lowerthan the reference voltage value, the output voltage value from theoutput terminal is increased. In case the measured voltage value ishigher than the reference voltage value, the output voltage value fromthe output terminal is decreased.

The source of the p-type MOSFET 11A is connected to the constant currentsource 12A. The drain of the p-type MOSFET 11A is connected to theground potential Vss of the integrated circuit main body 16A. The gateof the p-type MOSFET 11A is set to an arbitrary voltage 17A below thesource voltage Vdd of the integrated circuit main body 16A. Thedifference between the source voltage Vdd of the integrated circuit mainbody 16A and the arbitrary voltage 17A is always constant. Here, thedifference is set to 0.4 V.

That is, the gate voltage of the p-type MOSFET 11A is 0.6 V. The voltagevalue of the reference input IN1 of the comparator section 13A is set tothe source voltage Vdd of the integrated circuit main body 16A. Themeasured input IN2 of the comparator section 13A is connected to thesource of the p-type MOSFET 11A. The output of the comparator section13A is connected to the substrate voltage BP of the p-type MOSFET 11A.The upper limit of the output range of the comparator section 13A isequal to or above the source voltage Vdd of the integrated circuit mainbody 16A and the lower limit is below the source voltage Vdd of theintegrated circuit main body 16A.

Assume that the output range of the comparator section 13A is a voltagerange of 0.6 V through 2.0 V.

It is possible to output the substrate voltage BP via a limiter 19A(limiting means) which uses the upper or lower limit value of the outputrange of the comparator section 13A as a limit voltage value.

An example will be described where the comparator section 13A to outputthe substrate voltage BP on the PMOS comprises a limiter 19A.

FIG. 2 is a circuit diagram showing an example of the comparator section13A comprising a limiter 19A.

As shown in FIG. 2, the comparator section 13A comprises an operationalamplifier 18A and the limiter 19A. The limiter 19A comprises registers111A, 112A, comparators 113A, 114A, and MOSFETs 115A, 116A for thelimiter.

Next, a method for determining a limit voltage value by way of thelimiter 19A will be described.

In the semiconductor integrated circuit apparatus 10A which hasundergone the fabrication process, the potential difference between thesource and the drain is transitioned toward negative values from 0. Thevoltage value obtained when the drain current Ids of the p-type MOSFET11A has reached its minimum value is stored into the register 111A.

Next, the potential difference between the source and the substrate istransitioned toward positive values from 0. The voltage value obtainedwhen the drain current Ids of the p-type MOSFET 11A has reached itsmaximum value is stored into the separate register 112A.

It is possible to provide the upper limit of the substrate voltage BP bycomparing, on the comparator 113A, the voltage value stored in theregister 111A (upper limit voltage) and the voltage BP to be output andturning on/off the MOSFET 115A for the limiter the gate of which isconnected to the output of the comparator 113A.

The upper limit of the substrate voltage BP (upper limit of the outputvoltage value of the substrate voltage regulating means) is preferablyset to a voltage within a range where the GIDL effect does not occur inthe p-type MOSFET 11A.

It is possible to provide the lower limit of the substrate voltage BP bycomparing on the comparator 114A, the voltage value stored in theregister 112A (lower limit voltage) and the voltage BP to be output andturning on/off the MOSFET 115A for the limiter the gate of which isconnected to the output of the comparator 114A.

When an excessive negative substrate voltage (back bias) is applied, thepolarity of the feedback gain of the circuit 14A generating a constantthreshold value (Vth) is changed by way of the GIDL effect, thus causingdeadlock in the feedback system, a phenomenon where appropriate feedbackis not applied thus stabilizing the feedback system in an abnormalstate.

As a reference, FIG. 3 shows FIG. 8 representing the Ids-Vgscharacteristics in Hiroyuki Mizuno and seven others, “An 18-μA StandbyCurrent 1.8-V, 200 MHz Microprocessor with Self-Substrate-BiasedData-Retention Mode”, NOVEMBER 1999, IEEE JOURNAL OF SOLID-STATECIRCUITS, VOL. 34, No. 11, p. 1392-1500. In FIG. 3, for Vbb=−2.3V withlarge back bias, the drain current due to the GIDL effect is high.

Note that the feedback system may be subject to deadlock depending onthe arrangement of a circuit source.

When an excessive positive substrate voltage (forward bias) is applied,the MOSFET shows the bipolar characteristics and the feedback gain ofthe circuit 14A generating a constant threshold value (Vth) increases toa large extent and the feedback system becomes more likely to oscillate.

FIG. 4 shows the simulation values of the drain current Ids obtainedwhen the substrate voltage Vbs of the p-type MOSFET is varied. AS shownin FIG. 4, applying a forward bias exceeding a predetermined voltage(minus direction in FIG. 4) to the MOSFET causes the drain current Idsto decrease.

Thus, it is important that the limit voltage to prevent deadlock and thelimit voltage to prevent oscillation of the feedback system arereflected onto the limit voltage value.

In order to prevent deadlock and oscillation of the feedback systemmentioned above, the lower limit of the substrate voltage BP (lowerlimit of the output voltage value of the substrate voltage regulatingmeans) is preferably set to a voltage in the range where the p-typeMOSFET 11A does not show the bipolar characteristics. The upper limit ofthe substrate voltage BP (upper limit of the output voltage value of thesubstrate voltage regulating means) is preferably set to a voltage inthe range where the GIDL effect does not occur in the p-type MOSFET 11A.

While the limit voltage value is stored into the registers 111A, 112A,the limit voltage value may be set to a fixed voltage value obtainedthrough a trimming technique and input to the comparators 113A, 114A.

The characteristics of the semiconductor integrated circuit apparatus10A which has undergone the fabrication process may be stored in aseparate index database in advance and the above limit voltage value maybe determined at an arbitrary measurement point alone.

To reflect secular change after fabrication, the above method fordetermining a limit voltage value may be applied to the semiconductorintegrated circuit apparatus 10A as required to change the limit voltagevalue.

For example, assuming that the measured voltage is 1.1 V when thesubstrate voltage BP of the p-type MOSFET 11 is 1 V, the output voltageof the comparator section 13 will drop and regulation is made so thatthe measured voltage will be 1 V.

The circuit 14A generating a constant threshold value (Vth) controls thesource-substrate voltage value of MOSFET so that the drain current foran arbitrary gate voltage value in a subthreshold region will be freefrom temperature dependence and process variation dependence. Theobtained value of the drain current shows that the threshold value ofthe plurality of p-type MOSFETs arranged on the integrated circuit mainbody 16A is constant.

Second Embodiment

FIG. 5 is a circuit diagram showing semiconductor integrated circuitapparatus 10B according to the second embodiment. As shown in FIG. 5,the semiconductor integrated circuit apparatus 10B comprises a circuit14A generating a constant threshold value (Vth) (substrate voltageregulating means) including monitor means 15B including an n-type MOSFET11B and a constant current source 12B and a comparator section 13B(comparison means), and an integrated circuit main body 16B.

In the second embodiment, the threshold value Vth of the MOSFET is Vgs(gate-source voltage) obtained for example in case Ids=50 nA×(W/L) whenVDD=1 V. The Ids is a source-drain current of MOSFET, W is the channelwidth of MOSFET, and L is the channel length of MOSFET.

The n-type MOSFET 11B is arranged on the same substrate as theintegrated circuit main body 16B. In this embodiment, the transistorsize of the n-type MOSFET 11B is: channel width W=1.2 μm, channel lengthL=0.12 μm.

The constant current source 12B and the comparator section 13B may be ormay not be arranged on the same substrate as the integrated circuit mainbody 16B.

The constant current source 12B uses a material which is “nottemperature dependent” and is composed of for example a band gapreference circuit showing the constant current characteristics. The term“not temperature dependent” is defined equal to or below 20 PPM/° C.(which does not mean “temperature independent”). The constant currentsource 12B supplies a current of 500 nA.

The comparator section 13B comprises for example an operationalamplifier and an OTA. To the input terminal of the comparator section13B are input at least a reference voltage value and a measured voltagevalue. The reference voltage value and the measured voltage value arecompared with each other. In case the measured voltage value is lowerthan the reference voltage value, the output voltage value from theoutput terminal is increased. In case the measured voltage value ishigher than the reference voltage value, the output voltage value fromthe output terminal is decreased.

The drain of the n-type MOSFET 11B is connected to the constant currentsource 12B. The source of the n-type MOSFET 11B is connected to theground potential Vss of the integrated circuit main body 16B. The gateof the n-type MOSFET 11B is set to an arbitrary voltage 17B equal to orabove the ground voltage Vss of the integrated circuit main body 16B.The difference between the source voltage Vdd of the integrated circuitmain body 16B and the arbitrary voltage 17B is always constant. Here,the difference is set to 0.4 V.

The voltage value of the reference input IN1 of the comparator section13B is set to the source voltage value of the integrated circuit mainbody 16B. The measured input IN2 of the comparator section 13B isconnected to the drain of the n-type MOSFET 11B. The output of thecomparator section 13B is connected to the substrate of the n-typeMOSFET 11B. The upper limit of the output range of the comparatorsection 13B is equal to or above the ground potential of thesemiconductor integrated circuit apparatus 10B and the lower limit isbelow ground potential of the semiconductor integrated circuit apparatus10B.

Assume that the output range of the comparator section 13B is a voltagerange of −1.0 V through 0.4 V.

It is possible to output the substrate voltage BP via a limiter 19B(limiting means) which uses the upper or lower limit value of the outputrange of the comparator section 13B as a limit voltage value.

An example will be described where the comparator section 13B to outputthe substrate voltage BN on the NMOS comprises a limiter 19B.

FIG. 6 is a circuit diagram showing an example of the comparator section13B comprising a limiter 19B.

As shown in FIG. 6, the comparator section 13B comprises an operationalamplifier 18B and the limiter 19B. The limiter 19B comprises registers111B, 112B, comparators 113B, 114B, and MOSFETs 115B, 116B for thelimiter.

Using such an output circuit allows a current to be supplied stably upto the neighborhood of a limit value. A substrate voltage is stablyobtained in a forward bias mode when a current flows into a source via asubstrate, which is especially effective in the stable operation of atarget circuit.

A minus voltage is in advance generated by a minus booster circuit, anda configuration such that the applied voltage is input to a part whereVDD is equal to −3V is adopted, then the response capability of thefeedback loop will be good. If the boosted circuit is used in a finalbuffer, characteristics of the feedback loop will be discrete and theresponse capability will become worse, because of its generating clock.

Next, a method for determining a limit voltage value by way of thelimiter 19B will be described.

In the semiconductor integrated circuit apparatus 10B which hasundergone the fabrication process, the potential difference between thesource and the drain is transitioned toward negative values from 0. Thevoltage value obtained when the drain current Ids of the n-type MOSFET11B has reached its minimum value is stored into the register 111B.

Next, the potential difference between the source and the substrate istransitioned toward positive values from 0. The voltage value obtainedwhen the drain current Ids of the n-type MOSFET 11B has reached itsmaximum value is stored into the separate register 112B.

It is possible to provide the upper limit of the substrate voltage BN bycomparing, on the comparator 113B, the voltage value stored in theregister 111B (upper limit voltage) and the voltage BN to be output andturning on/off the MOSFET 115B for the limiter the gate of which isconnected to the output of the comparator 113B.

The upper limit of the substrate voltage BN is preferably set to avoltage within a range where the n-type MOSFET 11A does not show thebipolar characteristics.

It is possible to provide the lower limit of the substrate voltage BN bycomparing, on the comparator 114B, the voltage value stored in theregister 112B (lower limit voltage) and the voltage BN to be output andturning on/off the MOSFET 115B for the limiter the gate of which isconnected to the output of the comparator 114B.

When an excessive negative substrate voltage (back bias) is applied, thepolarity of the feedback gain of the circuit 14B generating a constantthreshold value (Vth) is changed by way of the GIDL effect, thus causingdeadlock in the feedback system, a phenomenon where appropriate feedbackis not applied thus stabilizing the feedback system in an abnormalstate.

Note that the feedback system may be subject to deadlock depending onthe arrangement of a circuit source.

When an excessive positive substrate voltage (forward bias) is applied,the MOSFET shows the bipolar characteristics and the feedback gain ofthe circuit 14A generating a constant threshold value (Vth) increases toa large extent and the feedback system becomes more likely to oscillate.

FIG. 7 shows the simulation values of the drain current Ids obtainedwhen the substrate voltage Vbs of the n-type MOSFET is varied. AS shownin FIG. 7, applying a forward bias exceeding a predetermined voltage(minus direction in FIG. 7) to the MOSFET causes the drain current Idsto decrease.

Thus, it is important that the limit voltage to prevent deadlock and thelimit voltage to prevent oscillation of the feedback system arereflected onto the limit voltage value.

The lower limit of the substrate voltage BN is preferably set to avoltage in the range where the GIDL effect does not occur in the n-typeMOSFET 11B. The upper limit of the substrate voltage BN (upper limit ofthe output voltage value of the substrate voltage regulating means) ispreferably set to a voltage in the range where the n-type MOSFET 11Bdoes not show the bipolar characteristics.

While the limit voltage value is stored into, the registers 111B, 112B,the limit voltage value may be set to a fixed voltage value obtainedthrough a trimming technique and input to the comparators 113B, 114B.

The characteristics of the semiconductor integrated circuit apparatus10B which has undergone the fabrication process may be stored in aseparate index database in advance and the above limit voltage value maybe determined at an arbitrary measurement point alone.

To reflect secular change after fabrication, the above method fordetermining a limit voltage value may be applied to the semiconductorintegrated circuit apparatus 10B as required to change the limit voltagevalue.

The circuit 14B generating a constant threshold value (Vth) controls thesource-substrate voltage value of MOSFET so that the drain current foran arbitrary gate voltage value in a subthreshold region will be freefrom temperature dependence and process variation dependence. Theobtained value of the drain current shows that the thresholds value forthe plurality of n-type MOSFETs arranged on the integrated circuit mainbody 16 is constant.

FIG. 23 is a configuration example in which the characteristics of theconstant current source 12B shown in FIG. 5 have been furtherapproximated to ideal current source characteristics.

The configuration is as follows. The gate of a MOSFET 233 having atleast the same channel length L and channel width W as a MOSFET 234 tobe monitored is set to have the same potential as the source potentialof the MOSFET 233. A current mirror circuit 232 taking its source fromthe drain current of the MOSFET 233 is then added in parallel to theconstant current source 12B in FIG. 5. Additionally, a predeterminedvoltage value is applied to each of input terminals 235, 236. Referencenumeral 237 denotes an operational amplifier.

If this current source 231 is absent, when the substrate voltage valueof a monitor device becomes lower than −0.4 V, usually, the GIDL effectcauses leakage to increase, leading to an increase in amount of avirtual current. Thus, the applied voltage of the substrate voltagevalue will be increased by such an amount of increase.

However, in this current source 231, a term of GIDL is cancelled, sothat it becomes possible to obtain a pure threshold value or saturationcurrent of MOSFET, thus applying the substrate voltage BN regulated tohigher accuracy than in the configuration using the constant currentsource 12B.

Then, when a positive substrate voltage (forward bias) is applied, thebipolar effect causes leakage of the MOSFET 234 to increase, but it ispossible to cancel such an increase.

Furthermore, FIG. 24 shows p-well regions that provide the substrates ofthe n-type MOSFETs 233, 234 shown in FIG. 23. The p-well region thatprovides the substrate of the n-type MOSFET 233 and the p-well regionthat provides the substrate of the n-type MOSFET 234 are separated, asshown in FIG. 24, as an n-well region is formed therebetween.

Besides, FIG. 25 shows a configuration example in which the constantcurrent source 12A shown in FIG. 1 has also been approximated to idealcurrent source characteristics similarly to FIG. 23.

The configuration is as follows. The gate of a MOSFET 253 having atleast the same channel length L and channel width W as a MOSFET 254 tobe monitored is set to have the same potential as the source potentialof the MOSFET 253. A current mirror circuit 252 taking its source fromthe drain current of the MOSFET 253 is then added in parallel to theconstant current source 12A in FIG. 1. Additionally, a predeterminedvoltage value is applied to each of input terminals 255, 256. Referencenumeral 257 denotes an operational amplifier.

Third Embodiment

FIG. 8 is a circuit diagram showing semiconductor integrated circuitapparatus 20A according to the third embodiment. As shown in FIG. 8, thesemiconductor integrated circuit apparatus 20A comprises a circuit 24Agenerating a constant drain current (substrate voltage regulating means)including monitor means 25A including a p-type MOSFET 21A and a constantcurrent source 22A and a comparator section 23A (comparison means), andan integrated circuit main body 26.

In the third embodiment, assume that the saturation current of MOSFET isfor example a source-drain current obtained when Vgs=1 V, VDD=1 V, andVss=0.

The circuit 24A generating a constant drain current (Ids) is a circuit(substrate voltage regulating means) which controls the substratevoltage of MOSFET so that the drain current for an arbitrary gatevoltage value in the saturated region of MOSFET will be constant. Thetransistor size of the p-type MOSFET 21A is: channel width W=1 μm,channel length L=0.12 μm.

The constant current source 22A uses a material which is “nottemperature dependent” and is composed of for example a band gapreference circuit showing the constant current characteristics. The term“not temperature dependent” is defined equal to or below 20 PPM/° C.(which does not mean “temperature independent”). The constant currentsource 22A supplies a current of 300 μA.

The comparator section 23A comprises for example an operationalamplifier and an OTA. To the input terminal of the comparator section23A are input at least a reference voltage value and a measured voltagevalue. The reference voltage value and the measured voltage value arecompared with each other. In case the measured voltage value is lowerthan the reference voltage value, the output voltage value from theoutput terminal is increased. In case the measured voltage value ishigher than the reference voltage value, the output voltage value fromthe output terminal is decreased.

The source of the p-type MOSFET 21A is connected to the constant currentsource 22A. The drain of the p-type MOSFET 21A is connected to theground potential Vss of the integrated circuit main body 26. The gate ofthe p-type MOSFET 21A is connected to the ground potential Vss of theintegrated circuit main body 26.

The voltage value of the reference input IN1 of the comparator section23A is set to the source voltage Vdd of the integrated circuit main body26. The measured input IN2 of the comparator section 23A is connected tothe source of the p-type MOSFET 21A. The output of the comparatorsection 23A is connected to the substrate voltage BP of the p-typeMOSFET 21A. The upper limit of the output range of the comparatorsection 13A is equal to or above the source voltage Vdd of theintegrated circuit main body 26 and the lower limit is below the sourcevoltage Vdd of the integrated circuit main body 26.

Assume that the output range of the comparator section 23A is a voltagerange of 0.6 V through 2.0 V.

It is possible to output the substrate voltage BP via a limiter 19A(limiting means) which uses the upper or lower limit value of the outputrange of the comparator section 23A as a limit voltage value. The actionassumed in case limiting means is provided in this embodiment is thesame as that in the first embodiment.

The circuit 24A generating a drain current (Ids) controls the substratevoltage BP so that the drain current for an arbitrary gate voltage valuethe saturated region of MOSFET will be constant. The obtained value ofthe drain current shows that the drain current Ids for the plurality ofp-type MOSFETs arranged on the integrated circuit main body 26 isconstant.

Fourth Embodiment

FIG. 9 is a circuit diagram showing semiconductor integrated circuitapparatus 20B according to the fourth embodiment.

As shown in FIG. 9, the semiconductor integrated circuit apparatus 20Acomprises a circuit 24A generating a constant drain current (Ids)(substrate voltage regulating means) including monitor means 25Aincluding an n-type MOSFET 21B and a constant current source 22A and acomparator section 23A (comparison means), and an integrated circuitmain body 26A.

In the fourth embodiment, assume that the saturation current of MOSFETis for example a source-drain current obtained when Vgs=1 V, VDD=1 V,and Vss=0.

The circuit 24B generating a constant drain current (Ids) is a circuit(substrate voltage regulating means) which controls the substratevoltage of MOSFET so that the drain current for an arbitrary gatevoltage value in the saturated region of MOSFET will be constant. Thetransistor size of the n-type MOSFET 21B is: channel width W=1 μm,channel length L=0.12 μm.

The constant current source 22B uses a material which is “nottemperature dependent” and is composed of for example a band gapreference circuit showing the constant current characteristics. The term“not temperature dependent” is defined equal to or below 20 PPM/° C.(which does not mean “temperature independent”). The constant currentsource 22B supplies a current of 600 μA.

The comparator section 23B comprises for example an operationalamplifier and an OTA. To the input terminal of the comparator section23B are input at least a reference voltage value and a measured voltagevalue. The reference voltage value and the measured voltage value arecompared with each other. In case the measured voltage value is lowerthan the reference voltage value, the output voltage value from theoutput terminal is increased. In case the measured voltage value ishigher than the reference voltage value, the output voltage value fromthe output terminal is decreased.

The drain of the n-type MOSFET 21B is connected to the constant currentsource 22B. The source of the n-type MOSFET 21B is connected to theground potential Vss of the integrated circuit main body 26. The gate ofthe n-type MOSFET 21B is set the source voltage Vdd of the integratedcircuit main body 26.

The voltage value of the reference input IN1 of the comparator section23B is set to the source voltage Vdd of the integrated circuit main body26A. The measured input IN2 of the comparator section 23A is connectedto the source of the n-type MOSFET 21B. The upper limit of the outputrange of the comparator section 23B is equal to or above the groundpotential Vss of the integrated circuit main body 26 and the lower limitis below the ground potential Vss of the integrated circuit main body26.

Assume that the output range of the comparator section 23B is a voltagerange of −1.0 V through 2.0 V.

In this embodiment, same as the second embodiment, it is possible tooutput the substrate voltage BN via a limiter 19B (limiting means) whichuses the upper or lower limit value of the output range of thecomparator section 23B as a limit value. In this way, the action assumedin case limiting means is provided in this embodiment is the same asthat in the second embodiment.

The circuit 24B generating a drain current (Ids) controls the substratevoltage BN so that the drain current for an arbitrary gate voltage valuein the saturated region of MOSFET will be constant. The obtained valueof the drain current shows that the drain current Ids for the pluralityof n-type MOSFETs arranged on the integrated circuit main body 26 isconstant.

Fifth Embodiment

FIG. 10 is a circuit diagram showing semiconductor integrated circuitapparatus 30 according to the fifth embodiment. As shown in FIG. 10, thesemiconductor integrated circuit apparatus 30 comprises the circuits14A, 14B generating a constant threshold value (Vth) shown in the firstand second embodiments and integrated circuit main body 36 incorporatinga feedback buffer 31. The substrate voltages BP, BN of the circuits 14A,14B generating a constant threshold value (Vth) are connected to therespective substrate voltages of the n-type and p-type MOSFETS of thefeedback buffer 31 in the integrated circuit main body 36.

The advantage of using the circuits 14A, 14B generating a constantthreshold value (Vth) in this embodiment will be described with relationto the evaluation result by a specific example of the feedback buffer31. In this example, each MOSFET constituting the feedback buffer 31 hasthe following parameters:

Ids of p-type MOSFET=240 μm; Vth of p-type MOSFET=0.35 V;

Ids of n-type MOSFET=600 μA/μm; Vth of n-type MOSFET=0.35 V;

W of p-type MOSFET=2 μm; L of p-type MOSFET=0.12 μm;

W of n-type MOSFET=1 μm; L of n-type MOSFET=0.12 μm;

FIG. 11 shows static noise margin widths obtained through circuitsimulation (SPICE) using the circuits 14A, 14B generating a constantthreshold value (Vth), with the source voltage varied under fourconditions: 1) T=−40° C. (low temperature); substrate voltages BN, BP=0V; 2) T=−40° C. (low temperature); substrate voltages BN, BP=0.35 V(forward bias); 3) T=125° C. (high temperature); substrate voltages BN,BP=0 V; 4) T=125° C. (high temperature); substrate voltages BN, BP=−0.35V (back bias).

In FIG. 11, the horizontal axis represents the source voltage value ofthe feedback buffer 31, and the vertical axis represents the staticnoise margin width of the feedback buffer 31. As shown in FIG. 11, incase the circuits 14A, 14B generating a constant threshold value (Vth)are used, the width of variation of static noise margin widths isnarrower and stable operation is assured at low voltages.

FIG. 12 shows the temperature dependence of a leakage current assumed intwo cases: 1) the circuits 14A, 14B generating a constant thresholdvalue (Vth) are used for the substrate voltage of the feedback buffer31; and 2) the circuits 14A, 14B are not used for the substrate voltageof the feedback buffer 31.

In FIG. 12, the horizontal axis represents a temperature and thevertical axis a leakage current in logarithm. As shown in FIG. 12, theleakage current slightly increases at low temperatures but is reduceddramatically at high temperatures.

While the reference voltage is a low voltage of 0.4 V in this example,there may be a need to set a higher Vth in case the Vth is too low andthe static margin is reduced at a high voltage. In such a case,resistance division means may be provided in the reference voltagesection so that the reference voltage value will be some percentage ofthe applied voltage value.

A limit voltage circuit is further effective in varying the referencevoltage. For example, when a reference voltage of 0.35 V is set whenVDD=1 V, the ratio of the reference voltage to the applied voltage is35%. The reference voltage is 0.7 V when VDD=2 V. To provide the value,a further back bias must be applied thus resulting in the GIDL effect.To prevent this, the limit circuit is effective.

Sixth Embodiment

FIG. 13 is a circuit diagram showing semiconductor integrated circuitapparatus 40 according to the sixth embodiment. As shown in FIG. 13, thesemiconductor integrated circuit apparatus 40 comprises the circuits24A, 24B generating a constant drain current (Ids) shown in the firstembodiment and integrated circuit main body 46 incorporating a memorycircuit 41 (only one memory cell is shown). The substrate voltages BP,BN of the circuits 24A, 24B generating a constant drain current (Ids)are connected to the respective substrate voltages of the n-type andp-type MOSFETS of the memory circuit in the integrated circuit main body36.

The memory circuit 41 comprises at least a transfer gate including ann-type MOSFET 42, a memory storage device 43, a bit line 44, and a wordline 45. The memory storage device 43 may be a capacitor of DRAM or aCMOS inverter of SRAM. As the DRAM and SRAM are provided a large numberof memory circuits 41 shown in FIG. 13.

The drain of the n-type MOSFET 42 is connected to the memory storagedevice 43. The source of the n-type MOSFET 42 is connected to the bitline 44. The gate of the n-type MOSFET 42 is connected to the word line45.

In this way, the circuits 24A, 24B generating a constant drain current(Ids) supplies substrate voltages BP, BN to the integrated circuit mainbody 46 to control the voltage value across the source and substrate ofthe n-type MOSFET 42 in the memory circuit 41 and other p-type or n-typeMOSFETs (not shown) so that the drain current for an arbitrary gatevoltage value in a subthreshold region will be free from temperaturedependence and process variation dependence, thus preventing memory datafrom being corrupted due to a leakage current in the subthresholdregion.

Seventh Embodiment

FIG. 14 is a circuit diagram showing semiconductor integrated circuitapparatus 50 according to the seventh embodiment. As shown in FIG. 14,the semiconductor integrated circuit apparatus 50 comprises the circuits14A, 14B generating a constant threshold value (Vth) shown in the firstand second embodiments and integrated circuit main body 56 incorporatinga feedback buffer 31 incorporating an SRAM circuit 51 (only one memorycell is shown).

The substrate voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) are connected to the respective substratevoltages of the n-type and p-type MOSFETS of the SRAM circuit 51 in theintegrated circuit main body 56.

The advantage of using the circuits 14A, 14B generating a constantthreshold value (Vth) in this embodiment will be described with relationto the evaluation result by a specific example.

FIG. 15 shows the source voltage and the read noise margin of SRAM ateach of the high and low temperatures for a case where a substratevoltage is not applied and a case where a substrate voltage is appliedso that Vth will be constant.

FIG. 16 shows a similar graph of the temperature dependence of the writenoise margin of SRAM. The figure shows the effect of reduction of thetemperature dependence of the write noise margin at low voltages by theapplication of an optimum substrate voltage. That is, operation isallowed at low voltages thus reducing the power consumption of SRAM.

Eighth Embodiment

FIG. 17 is a circuit diagram showing semiconductor integrated circuitapparatus 60 according to the eighth embodiment.

As shown in FIG. 17, the semiconductor integrated circuit apparatus 60uses the output voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) as the substrate voltages of the timingborrow circuit 61. D in the timing borrow circuit 61 represents datainput and CLK clock input.

The static noise margin of the timing borrow circuit 61 is determined byVth of the n-type MOSFET. In other words, it is possible to reducetemperature dependence and process variation dependence by using thecircuits 14A, 14B generating a constant threshold value (Vth). As shownin the seventh embodiment, the leakage current is also reduced.

Ninth Embodiment

FIG. 18 is a circuit diagram showing semiconductor integrated circuitapparatus 70 according to the ninth embodiment.

As shown in FIG. 18, the semiconductor integrated circuit apparatus 70uses the output voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) as the substrate voltages of the MOSFETsof the differential operational amplifier 71 in the integrated circuitmain body 76. In case the Vth of the n-type MOSFETs are varied, theoutput voltage of the differential operational amplifier is above Vth sothat the output voltage depends on Vth.

However, in case the circuits 14A, 14B generating a constant thresholdvalue (Vth) are used, Vth is kept constant so that the output voltage ofthe differential operational amplifier does not depend on Vth but isconstant. With this configuration, the temperature dependence andprocess variation dependence of the lower limit voltage in the outputrange of the differential operational amplifier are reduced.

Tenth Embodiment

FIG. 19 is a circuit diagram showing semiconductor integrated circuitapparatus 80 according to the tenth embodiment.

As shown in FIG. 19, the semiconductor integrated circuit apparatus 80uses the output voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) as the substrate voltages of the MOSFETsof the VCO (Voltage-controlled Oscillator) 81 in the integrated circuitmain body 86. In case the gate of the MOSFET to supply a bias voltagedepends on a threshold value, the frequency response with respect to theinput voltage is varied.

By using the output of the circuits generating a constant thresholdvalue (Vth) as the substrate voltage of the MOSFET, the temperaturedependence and process variation dependence of the frequency responsewith respect to the input voltage are reduced.

The circuit shown in FIG. 19 is an example. The tenth embodiment isapplicable to all VCOs where the input voltage is input to the gate ofMOSFET.

Eleventh Embodiment

FIG. 20 is a circuit diagram showing semiconductor integrated circuitapparatus 90 according to the eleventh embodiment.

As shown in FIG. 20, the semiconductor integrated circuit apparatus 90uses the output voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) as the substrate voltage of the CMOSlogic circuit 91 in the integrated circuit main body 96. The delay valueof the CMOS logic circuit 91 is di/dt=CV so that the temperaturedependence and process variation dependence of delay are reduced.

The circuit shown in FIG. 20 is an example of CMOS logic circuit. Theeleventh embodiment is applicable to all CMOS logic circuits of anylogic configuration.

Twelfth Embodiment

FIG. 21 is a circuit diagram showing semiconductor integrated circuitapparatus 100 according to the tenth embodiment.

As shown in FIG. 21, the semiconductor integrated circuit apparatus 100uses the output voltages BP, BN of the circuits 14A, 14B generating aconstant threshold value (Vth) as the substrate voltage of the inverterof the CCO (Current-controlled Oscillator) 101 in the integrated circuitmain body 106.

With this configuration, same as the eleventh embodiment, the delayvalue of the circuit is kept constant, thereby reducing the temperaturedependence and process variation dependence of the oscillating frequencyof the CCO 101.

Thirteenth Embodiment

FIG. 22 is a circuit diagram showing semiconductor integrated circuitapparatus 100 according to the thirteenth embodiment.

As shown in FIG. 22, in the circuits 121A, 121B generating a constant gm(transconductance:the ratio of the variation in the drain current withrespect to the variation in the gate voltage), the gate and the drainare connected to each other on the p-type MOSFET 122A and the n-typeMOSFET 122B. In case the gate and the drain are connected to each other,it is possible to approximate the substrate voltage to the gm of thetransistor.

By setting a desired voltage as the reference voltage of the operationalamplifier, it is possible to provide a circuit generating a constant gmin the neighborhood of a predetermined voltage value. By applying thisconfiguration to a circuit generating a constant gm of the transistor inthe integrated circuit main body 122, for example a current mirrorcircuit, it is possible to keep constant the gm of the transistor sothat the temperature dependence and process variation dependence of thesemiconductor integrated circuit apparatus will be eliminated.

Fourteenth Embodiment

The fourteenth embodiment will hereinafter be described. As an exampleof this embodiment, FIG. 26 shows an example of a multi-port registerfile such that the aforesaid circuit generating a constant thresholdvalue (Vth) and circuit generating a constant Ids are mounted togetherin the integrated circuit main body.

The multi-port register file 260 shown in FIG. 26 comprises a memorycell section 261 and a read data output circuit 262.

The circuit operation of this multi-port register file 260 willhereinafter be described.

In the memory cell section 261, when a write word line is activated,data is written thereinto via a write bit line.

Besides, a data read from the memory cell section 261 is performed suchthat when a read word line is activated, data is read out into a readbit line and this read data is further amplified by the read data outputcircuit and outputted to the external through an output terminal.

In this multi-port register file, the substrates of the individualMOSFETs, of the memory cell section 261 and of a keeper section 263 forholding the data in the read bit line, are connected to the circuitgenerating a constant threshold value (Vth).

Besides, the substrates of individual MOSFETs constituting the read dataoutput circuit 262 are connected to the circuit generating a constantIds.

Thus, in the multi-port register file 260 shown in FIG. 26, the circuitgenerating a constant threshold value (Vth) is used to regulate thesubstrate voltage of, for example, a circuit section having acomparatively low noise margin (or a sensitive circuit section) such asthe memory cell section 261. The circuit generating a constant Ids(drain current) is used in, for example, the read data output circuit262 that comprises a CMOS etc., has a comparatively high noise marginand is required for high-speed operation.

That is, the circuit generating a constant threshold value (Vth) is usedto regulate the substrate voltage of a portion having a noise marginlower than a predetermined value. The circuit generating a constant Ids(drain current) is used to regulate the substrate voltage of a portionhaving a noise margin higher than the predetermined value.

Thereby, stable operation can be realized without loosing the high-speedproperties of the integrated circuit main body. Furthermore, the delayand electrical power having less temperature dependence can be realized.

Next, the multi-port register file having the aforesaid configuration ofFIG. 26 is actually manufactured by way of trial and the measuredresults are shown in FIGS. 27 and 28.

FIG. 27 shows the temperature characteristics of the relative value ofdelay time for a data read (Normalized Delay).

FIG. 28 shows the temperature characteristics of the relative value ofcurrent consumption during operation (Normalized Current).

MBB (Mixed BB) is the measurement result obtained when the circuitgenerating a constant threshold value (Vth) is used for the memory cellsection 261 and the circuit generating a constant Ids (drain current) isused for the read data output circuit 262.

NBB is the measurement result obtained when the substrate voltage is notchanged without operating the circuit generating a constant thresholdvalue (Vth) or the circuit generating a constant Ids, that is, when thesubstrate potential is set to be equal in potential to a source voltageof MOSFET.

Upon trial manufacture, two wafers are made on an experimental basis: awafer subjected to a process condition such as to intentionally causethe threshold voltage to deviate about +10% from a target thresholdvoltage, and a wafer subjected to a process condition such as tointentionally cause the threshold voltage to deviate about −10% from atarget threshold voltage.

A plurality of chips are formed on these two wafers.

Under the condition that VDD=0.8 V and an operating frequency(Freq.)=100 MHz, the plurality of chips are each measured for thetemperature characteristics of delay time for a data read and thetemperature characteristics of current consumption during operation.

In the wafer subjected to the process condition of about −10% deviation,the relative value of a chip having the fastest delay time (FIG. 27) andthe relative value of a chip having the largest current consumptionduring operation (FIG. 28) are indicated by MBBmax and NBBmax,respectively. In the wafer subjected to the process condition of about+10% deviation, the relative value of a chip having the slowest delaytime (FIG. 27) and the relative value of a chip having the smallestcurrent consumption during operation (FIG. 28) are indicated by MBBminand NBBmin, respectively.

As seen from the result of FIG. 27, the difference between the maximumand minimum values of delay time in case where the substrate voltage isalways constant (NBB) is lower than the difference between the maximumand minimum values of delay time in case where the circuit generating aconstant threshold value (Vth) and the circuit generating a constant Idsare mounted together (MBB (Mixed BB)). For example, when the temperatureis 125° C., the aforesaid difference between the maximum and minimumvalues is reduced to about 75%.

Besides, as seen from the result of FIG. 28, the difference between themaximum and minimum values of current consumption duringhigh-temperature operation in case where the substrate voltage is alwaysconstant (NBB) is large. However, the aforesaid difference between themaximum and minimum values in case where the circuit generating aconstant threshold value (Vth) and the circuit generating a constant Idsare mounted together (MBB (Mixed BB) is reduced about 27% when thetemperature is 125° C. as compared with NBB.

Furthermore, an example that is applied to a general SRAM circuit willbe cited in FIG. 29 and described as another example such that theaforesaid circuit generating a constant threshold value (Vth) andcircuit generating a constant Ids are mounted together in the integratedcircuit main body.

As shown in FIG. 29, a memory section 291 and a peripheral section 292,whose respective substrates are separated from each other, areconfigured such that different substrate voltages are applicable.

That is, the circuit generating a constant threshold value (Vth) isconnected to the memory section 291 having a comparatively low noisemargin (or being sensitive). The circuit generating a constant Ids isconnected to the peripheral section 292 including a portion that has acomparatively high noise margin and is required for high-speed operationof an input/output circuit or the like.

As aforesaid, in the fourteenth embodiment, the circuit generating aconstant threshold value (Vth) and the circuit generating a constant Idsare mixed together and thus applied to regulation of the substratepotentials of various circuit sections, thereby enabling optimization ofthe characteristics of each circuit.

Fifteenth Embodiment

FIG. 30 is a diagram showing in schematic form the circuit layout of anintegrated circuit main body 300 of the fifteenth embodiment.

The integrated circuit main body 300 of this embodiment has its circuitregion divided into a plurality of (four) regions that are areas A to D.

The circuit generating a constant threshold value (Vth) and the circuitgenerating a constant Ids are (or only any one of them may be) providedinside each of the areas A to D or in the vicinity of each of theregions.

The circuit generating a constant threshold value (Vth) and the circuitgenerating a constant Ids, which regulate the substrate potential ofeach of the regions, are thus provided in each of the areas A to D.Therefore, when there exist the local dependence of the ion dope of thedrain and source at the time of MOSFET device formation, the localdependence of a gate oxide film pressure, or the like, MOSFETcharacteristics become different in each of the areas A to D.

Consequently, since monitor means inside each of the areas A to Dreflects the characteristics of a MOSFET within the correspondingregion, it is possible to appropriately regulate the substrate potentialin correspondence to each of the areas A to D. Thus, it is possible toremove the nonuniformity of Vth and Ids of MOSFETs within the integratedcircuit main body 300.

The plural monitor means of the circuit generating a constant thresholdvalue (Vth) and the circuit generating a constant Ids for regulating thesubstrate potential may be provided inside of the each areas. Thesemonitor means may connected in parallel, each of the monitor means maybe monitored in time division. Further, if the monitor means aredisplaced in center and four corners of the area, it will be moreeffective.

Sixteenth Embodiment

FIG. 31 is a diagram showing in schematic form the configuration of thesixteenth embodiment. As shown in FIG. 31, in this embodiment, anintegrated circuit main body 310 is connected in which are mountedtogether (two in the example of the figure) MOSFET groups 315 (ahigh-Vth MOSFET), 316 (a low-Vth MOSFET) of the kinds different indevice characteristics (substrate voltage dependence).

The aforesaid MOSFET groups 315, 316 comprise MOSFETs havingsubstantially the same device characteristics. An output BPH of acircuit 311 generating a constant threshold value (Vth) of the p-typeMOSFET and an output BNH of a circuit 312 generating a constantthreshold value (Vth) of the n-type MOSFET, for regulating the high-VthMOSFET, are connected to provide the substrate voltage of the MOSFETgroup 315.

Besides, an output BPL of a circuit 311 generating a constant thresholdvalue (Vth) of the p-type MOSFET and an output BNL of a circuit 312generating a constant threshold value (Vth) of the n-type MOSFET, forregulating the low-Vth MOSFET, are connected to provide the substratevoltage of the MOSFET group 316.

The monitor sections of the circuits 311, 312 generating a constantthreshold value (Vth) use devices 315 a, 315 b corresponding to Vth ofthe MOSFET group 315 to which a substrate voltage is applied. Themonitor sections of the circuits 313, 314 generating a constantthreshold value (Vth) use devices 316 a, 316 b corresponding to Vth ofthe MOSFET group 316 to which a substrate voltage is applied.

By adopting such a configuration as aforesaid, it is possible to apply asubstrate voltage value suitable for the threshold value (Vth), Idsvalue, and gm value required by individual MOSFETs different in devicecharacteristics (substrate voltage dependence). Thus, distortion willnot occur in a circuit noise margin or the like, so that stableoperation can be realized.

Seventeenth Embodiment

The seventeenth embodiment has a frequency-voltage conversion circuit.The configuration is made such that the output of this frequency-voltageconversion circuit is applied to the gate of the MOSFET constituting themonitor means of the substrate voltage regulating means.

FIG. 32 is a block diagram showing, as an example of this embodiment, anexample in which the frequency-voltage conversion circuit 321 isconnected to an input terminal 322 (corresponding to 17A of FIG. 1 forexample) of a circuit 323 generating a constant threshold value (Vth).

A clock division circuit (or clock multiplication circuit) 326 foroutputting a clock obtained by dividing (or multiplying) a clockprovided from a clock oscillator 325 is connected to the input terminalof the frequency-voltage conversion circuit 321 so that an output clockof the clock division circuit 326 is inputted.

Additionally, instead of using this clock division circuit (or clockmultiplication circuit) 326, a clock of the clock oscillator 325 may beinputted as it is. Otherwise, the output of the clock division circuit(or clock multiplication circuit) may be connected to the clock input ofan integrated circuit main body 324. Clocks originating from the sameclock oscillating source (clock oscillator 325) need only be supplied tothe integrated circuit main body 324 and frequency-voltage conversioncircuit 321 so that a clock to be supplied to the integrated circuitmain body 324 is matched in phase with a clock to be supplied to thefrequency-voltage conversion circuit 321.

Besides, as shown in the graph of FIG. 33, the frequency-voltageconversion characteristic of the aforesaid frequency-voltage conversioncircuit 321 is a characteristic such that a clock frequency inputted isconverted into an output voltage value with a positive gradient.

Then, the frequency-voltage conversion circuit 321 comprises, forexample, a D-A converter or a DC-DC conversion circuit.

With the aforesaid configuration, in this embodiment, the thresholdvalue (Vth) regulated by the circuit generating a constant thresholdvalue (Vth) can be set to be higher at the time of a clock low frequencythan at the time of a clock high frequency for the integrated circuitmain body 324. Thus, there is the advantage of reducing MOSFET deviceleakage during the use at a low frequency.

Additionally, the example in which the frequency-voltage conversioncircuit 321 is a sequential circuit has been shown here. However, thecircuit configuration or the like may be simplified to output a discretevalue.

Besides, when the monitor means is a p-type MOSFET, as a matter ofcourse, the frequency-voltage conversion circuit need only be configuredsuch that the relationship between a frequency and an output voltage hasa negative gradient.

Further, in this embodiment, example of application of thefrequency-voltage conversion circuit in case that the substrate voltageregulating means is the circuit generating a constant threshold value(Vth), is described as aforementioned. However, in case that thesubstrate voltage regulating means is a GM constant circuit, if a valueof the current source in 121 of FIG. 22 source is varied by thefrequency-voltage conversion circuit, needless to say, same effect ascase of the circuit generating a constant threshold value (Vth) can begained.

Eighteenth Embodiment

As shown in FIG. 34A, the eighteenth embodiment is characterized by thefollowing in the relationship between an electric capacity CB betweenthe substrate voltage BN of the n-type MOSFET within the integratedcircuit main body and the ground potential Vss of the n-type MOSFET, andan electric capacity CA between the aforesaid substrate voltage BN andthe substrate potential BP of the p-type MOSFET. That is, in such arelationship, a capacity component CC is added between these BN and BP.

FIG. 35 is a schematic diagram showing an example of a configuration forrealizing this embodiment.

In an integrated circuit main body of this embodiment, an n-well region351 is configured on a P substrate and a p-well region 352 is configuredon this n-well region 351.

A p-type MOSFET constituting the integrated circuit main body exits onthis n-well region 351, and the source voltage Vdd is connected via acontact hole 355 a to a source 354 of a p-type MOSFET 353.

Besides, the substrate voltage BP is connected via a contact hole 355 bto the p-well region 352, and the ground potential Vss is connected viaa contact hole 355 c to a source 359 of an n-type MOSFET 356 provided onthe p-well region 352.

Furthermore, the substrate voltage BN is connected via a contact hole355 d to the n-well region 351. Additionally, reference character Gdenotes a gate of MOSFET.

A plurality of such p-type MOSFETs 353 and n-type MOSFETs 356 asaforesaid exist in the integrated circuit main body, and the individualMOSFETs also have the same configuration.

In the conventional integrated circuit, the BN-BP electric capacity CAbecomes higher than the aforesaid BN-Vss electric capacity CB. Thereason is that the area of a region in which the n-well region 351 makescontact with the p-well region 352 is far higher than the area of aregion in which the source 354 makes contact with the p-well region 352.

In case where the electric capacity CB is thus lower, when BN is varied,this variation is difficult to transmit to Vss, so that the variation ofBN and the variation of Vss are reduced to such profiles as shown inFIG. 34B.

In the example of this embodiment shown in FIG. 35, as shown on theright as seen in the figure, the ground potential Vss is connected via acontact hole 355 e to an n-well region 357 that is separated from then-well region 351 formed with MOSFETs so as not to short with BP.

Besides, a p-well region 358, provided in this n-well region 357, isconnected via a contact hole 355 f to BN, and the capacity component CCobtained by the connection is added to the BN-Vss electric capacity CB.

In this embodiment, the BN-Vss electric capacity is thus increased toCB+CC. Therefore, the variation produced when BN is varied is easy totransmit to Vss and as shown in FIG. 34C, BN and Vss are varied in thesame phase. Thus, a potential difference Vns between BN and Vss becomeslikely to be constant, so that the circuit operation of the integratedcircuit main body is stabilized.

Additionally, this capacity component CC may comprise the capacitycomponent of another portion other than the example shown in FIG. 35such as the capacity between wirings.

Next, FIG. 36 shows an example in which this capacity component CCcomprises a gate capacity.

As shown in FIG. 36, there is provided a MOSFET 361 that is not involvedin the circuit operation of the integrated circuit main body. The gateof this MOSFET 361 is connected to BN, while the source, drain, andsubstrate thereof are connected to Vss.

When the gate of the MOSFET 361 is connected to the side of a substratevoltage applied to the integrated circuit main body, the capacity alwaysbecomes constant on the negative bias side.

Besides, on the positive bias side, the capacity value is slightlyreduced, but there are the bipolar effect of a MOSFET substrate and acurrent component flowing from a substrate to a source. Therefore, thevariation of BN and Vss becomes likely to have the same phase, so thatthe integrated circuit main body is stably operated.

Furthermore, more preferably, when the BN-Vss electric capacity CB+CC isset to be higher than the BP-BN electric capacity CA, the aforesaidintegrated circuit main body is made more reliable in its stableoperation.

Nineteenth Embodiment

The nineteenth embodiment is set as follows. A variable voltage isapplied to the gate (17A) of the monitoring MOSFET 11A of the circuitgenerating a constant threshold value (Vth) that is the substratevoltage regulating means shown in FIG. 1, so as to provide a moregradual gradient than the temperature gradient of the threshold value(Vth) formed when a voltage applied to the aforesaid gate (17A) is setto be constant.

Conventionally, since the threshold value (Vth) of MOSFET decreasestogether with the temperature, when a constant voltage is applied to thegate 17A, the substrate voltage BP lowers as the temperature rises. Onthe contrary, in this embodiment, a variable voltage is applied to thegate 17A so as to provide a negative gradient against a rise intemperature.

For example, in FIG. 1, the temperature dependence of the substratevoltage BP, obtained when a constant voltage is applied to the gate 17Athat is the gate of the monitoring MOSFET 11A, is reduced to an inclinesuch as shown by the dashed line of FIG. 37A. However, when a variablevoltage having a negative gradient against the temperature (the higherthe temperature is, the applied voltage is reduced) is applied to thegate 17A, the temperature dependence of the substrate potential BP isreduced as shown by the solid line of FIG. 37A.

By such setting, the temperature dependence of the substrate voltageregulating means, for making regulation such that the threshold values(Vth) of individual MOSFETs within the integrated circuit main body ofFIG. 1 are constant, can be made lower than when the gate 17A has aconstant voltage. Thus, the aforesaid threshold values (Vth) of theindividual MOSFETs can be made uniform in a wider temperature range.

A voltage application circuit for applying to the gate 17A a variablevoltage having a negative gradient against the temperature need onlyuse, for example, the band gap reference circuit.

Besides, the configuration may be made such that a variable voltagehaving a negative gradient is applied to the gate 17A until thetemperature reaches a predetermined value and the voltage value becomesconstant when the temperature reaches the predetermined value or more.For example, the configuration need only be made such that a temperaturedetection circuit is added and the limiter acts on the voltage when thetemperature reaches a certain value or more.

In this embodiment, in the integrated circuit main body to which isadapted the circuit generating a constant threshold value (Vth), thegain of the integrated circuit main body due to a reduction in junctioncapacity of MOSFET can be reduced on a high temperature side, i.e., inthe sate where a substrate voltage is negatively applied. Besides,variations in threshold value of individual MOSFETs within theintegrated circuit main body can be suppressed even when the temperatureis varied.

When variations in threshold value (Vth) are thus reduced, variations inswitching rate of individual MOSFETs are reduced. Therefore, as shown inFIG. 37B, even when the temperature is varied, it is possible to preventthe phenomenon that the range of variations in circuit delay is widened.

Further, in this embodiment, relation between the temperature and thevoltage in case that the substrate voltage regulating means is thecircuit generating a constant threshold value (Vth), is described asaforementioned. However, in case that the substrate voltage regulatingmeans is a GM constant circuit, the desired value of FIG. 22 can beapplied. If a value of the current in 121 of FIG. 22 source is varied bythe frequency-voltage conversion circuit, needless to say, same effectas case of the circuit generating a constant threshold value (Vth) canbe gained.

Twentieth Embodiment

The twentieth embodiment is configured as follows. The output of thelimiting means is connected to a voltage supply circuit for supplying asource voltage to the integrated circuit main body. The aforesaid sourcevoltage is raised when a substrate voltage is the upper limit voltage ormore, while the aforesaid source voltage is reduced when the substratevoltage is the lower limit voltage or less.

For example, in FIG. 38, the configuration is made such that an upperlimit comparison signal 384 and an lower limit comparison signal 385 areinputted from the comparator section 13A including the limiter 19A shownin FIG. 2 to a voltage supply circuit 383 for supplying a source voltageto the integrated circuit main body. The upper limit comparison signal384 is obtained by comparing the upper limit voltage value of theregister 111A and the value of the substrate potential BP through acomparator 381. The lower limit comparison signal 385 is obtained bycomparing the lower limit voltage value of the register 112A and thevalue of the substrate potential BP through a comparator 382.

Additionally, the comparators 381, 382 may use the comparator in thelimiter 19A.

In this embodiment, with the aforesaid configuration, if the substrateBP reaches the upper limit value or more, the upper limit comparisonsignal 384 is transmitted to the voltage supply circuit 383. Thereby,the voltage supply circuit 383 raises a source voltage to be outputted.

At this time, the step of raising the source voltage to be outputted maybe either discrete or sequential. When the step is discrete, dispersionpower on the order of about 10 mV is desirable. When the upper limitcomparison signal 384 has not been transmitted, the rise in the sourcevoltage is completed.

Besides, the voltage supply circuit 383 itself also has set therein asource voltage upper limit value for not allowing the source voltage torise to a predetermined voltage value or more. Even if this sourcevoltage upper limit value is reached, when the upper limit comparisonsignal 384 still continues to be transmitted, the source voltage to beoutputted is fixed to the source voltage upper limit value.

On the contrary, if the substrate voltage BP reaches the lower limitvalue or more, the limit comparison signal 385 is transmitted to thevoltage supply circuit 383. Thereby, the voltage supply circuit 383lowers the source voltage to be outputted.

Besides, the voltage supply circuit 383 itself also has set therein asource voltage lower limit value for not allowing a source voltage tolower to a predetermined voltage value or more. Even if this sourcevoltage lower limit value is reached, when the lower limit comparisonsignal 385 still continues to be transmitted, the source voltage to beoutputted is fixed to the source voltage lower limit value.Additionally, the source voltage lower limit value may not be set, oronly any one of the source voltage upper and lower limit values may beset.

As aforesaid, in this embodiment, the source voltage to be supplied tothe integrated circuit main body is made variable. Thereby, it ispossible to further secure the improvement in the threshold valuecharacteristics, saturation current characteristics and gmcharacteristics of MOSFET by the substrate voltage regulating means.

Additionally, needless to say, the comparator section 13B including thelimiter 19B, shown in FIG. 6, that is the comparator having thesubstrate potential BP may be applied to FIG. 38.

The invention is not limited to the foregoing embodiments but may bemodified without departing from the spirit and scope thereof.

As mentioned hereinabove, the semiconductor integrated circuit apparatusaccording to the first aspect of the invention comprises: an integratedcircuit main body including a plurality of MOSFETs on a semiconductorsubstrate; monitor means for monitoring at least one of the draincurrents of the plurality of MOSFETs; and substrate voltage regulatingmeans for controlling the substrate voltage of the semiconductorsubstrate so as to keep constant the drain current. With thisconfiguration, it is possible to reduce the temperature dependence of adrain current in case there occurred a variation in the temperature ofthe semiconductor integrated circuit apparatus and reduce variations inthe characteristics of the semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence). Thisenhances the stable operation of the semiconductor integrated circuitapparatus.

According to the second aspect of the invention, when circuits anddevices having different characteristics are present within thesemiconductor integrated circuit, or the like, the plurality ofsubstrate voltage regulating means can be regulated to a substratevoltage suitable for the individual circuits and devices.

According to the third aspect of the invention, it is possible torealize stable circuit operation and furthermore to prevent reversion oftemperature dependence of delay time under a low voltage. Thus, it ispossible to reduce a leakage current under high temperature. Besides, itis possible to increase circuit speed and furthermore to preventreversion of temperature dependence of delay time under a low voltage.Thus, it is possible to reduce a leakage current under high temperature.

According to the fourth aspect of the invention, it is possible to applyto each region a substrate voltage for obtaining an appropriatethreshold value and saturation current when the device characteristicsof MOSFETs within the semiconductor integrated circuit have localdependence. Thus, it is possible to reduce variations in circuitcharacteristics within the semiconductor integrated circuit.

According to the fifth aspect of the invention, it is possible to applyan appropriate substrate voltage, without deteriorating a circuit noisemargin, to each of MOSFET groups different in device characteristics fora substrate voltage.

According to the sixth aspect of the invention, the drain current is adrain current for an arbitrary gate voltage value in a subthresholdregion or a saturated region. With this configuration, it is possible toreduce the temperature dependence of a drain current in case thereoccurred a variation in the temperature of semiconductor integratedcircuit apparatus and reduce variations in the characteristics of theindividual semiconductor integrated circuit apparatus created by afabrication process (process variation dependence). This enhances thestable operation of the semiconductor integrated circuit apparatus.

According to the seventh aspect of the invention, the gm of thetransistor is kept constant by the substrate voltage regulating means.It is thus possible to provide a circuit generating gm in theneighborhood of a predetermined voltage value thus keeping constant thegm of the transistor so that the temperature dependence and processvariation dependence of the semiconductor integrated circuit apparatuswill be eliminated.

According to the eighth aspect of the invention, the monitor meanscomprises a constant current source and a monitoring MOSFET formed onthe same substrate as the plurality of MOSFETs, the substrate voltageregulating means comprises comparison means for comparing the sourcepotential of the monitoring MOSFET with a predetermined referencepotential with the drain terminal of the monitoring MOSFET and the drainterminals of the plurality of MOSFETs connected to the ground potential,and the substrate voltage regulating means feeds back the output voltageoutput based on the comparison result by the comparison means to thesubstrate voltage of the monitoring MOSFET. With this configuration, itis possible to keep constant the threshold value (Vth) or drain current(Ids) of each of the plurality of MOSFETs arranged on the integratedcircuit main body. In this way, the threshold value (Vth) or draincurrent (Ids) of each of the MOSFETs is kept constant so that the draincurrent of the plurality of MOSFETs on the integrated circuit main bodyis regulated to an optimum value.

This regulation reduces the temperature dependence of a drain current incase there occurred a variation in the temperature of the semiconductorintegrated circuit apparatus and reduces variations in thecharacteristics of the semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence).

According to the ninth aspect of the invention, the reference potentialis a supply potential to the integrated circuit main body. It is thuspossible to keep constant the threshold value (Vth) or drain current(Ids) of each of the plurality of MOSFETs arranged on the integratedcircuit main body. In this way, the threshold value (Vth) or draincurrent (Ids) of each of the MOSFETs is kept constant so that the draincurrent of the plurality of MOSFETs on the integrated circuit main bodyis regulated to an optimum value.

This regulation reduces the temperature dependence of a drain current incase there occurred a variation in the temperature of the semiconductorintegrated circuit apparatus and reduces variations in thecharacteristics of individual semiconductor integrated circuit apparatuscreated by a fabrication process (process variation dependence).

According to the tenth aspect of the invention, the substrate voltageregulating means outputs a voltage value obtained by providing, by wayof limiting means, the upper and lower limits of the output voltageoutput based on the comparison result of the comparison means. It isthus possible to prevent a so-called “deadlock”, a phenomenon where anappropriate feedback is not applied to the substrate voltage of themonitoring MOSFET thus stabilizing the substrate voltage regulatingmeans in an abnormal state.

According to the eleventh aspect of the invention, the monitoring MOSFETis a p-type monitoring MOSFET, the upper limit of the output voltagevalue of the substrate voltage regulating means is set to a voltageequal to or above the supply potential of the integrated circuit mainbody and within a range where the GIDL effect does not occur in thep-type monitoring MOSFET, and the lower limit of the output voltagevalue of the substrate voltage regulating means is set to a voltagebelow the supply potential of the integrated circuit main body andwithin a range where the p-type monitoring MOSFET does not show thebipolar characteristics. It is thus possible to prevent the GIDL effectwhere the transistor characteristics are opposite to the regularcharacteristics as well as the bipolar characteristics where a forwardcurrent flows between the substrate and the drain thus reducing thedrain-source current, in case a large amount of substrate voltage isapplied.

According to the twelfth aspect of the invention, the monitoring MOSFETis an n-type monitoring MOSFET, the upper limit of the output voltagevalue of the substrate voltage regulating means is set to a voltageequal to or above the ground potential of the integrated circuit mainbody and within a range where the n-type monitoring MOSFET does not showthe bipolar characteristics, and the lower limit of the output voltagevalue of the substrate voltage regulating means is set to a voltagebelow the ground potential of the integrated circuit main body andwithin a range where the GIDL effect does not occur in the n-typemonitoring MOSFET. It is thus possible to prevent the GIDL effect wherethe transistor characteristics are opposite to the regularcharacteristics as well as the bipolar characteristics where a forwardcurrent flows between the substrate and the drain thus reducing thedrain-source current, in case a large amount of substrate voltage isapplied.

According to the thirteenth aspect of the invention, the source voltagesupplied to the integrated circuit main body can be made variable. Thus,it is possible to further secure the improvement in the threshold valuecharacteristics, saturation current characteristics, and gmcharacteristics of MOSFET by the substrate voltage regulating means.

According to the fourteenth aspect of the invention, the leakagecomponent of a parasitic bipolar or GIDL effect can be cancelled. Thus,it is possible to apply a substrate voltage capable of securing theoriginal threshold value and saturation current of the MOSFET of themonitor means.

According to the fifteenth aspect of the invention, it is possible toeliminate the leakage current component caused by the parasitic bipolareffect between the MOSFET of the monitor means and the leakage currentcanceling MOSFET. Thus, it is possible to apply a substrate voltage atwhich the original threshold value and saturation current of the MOSFETof the monitor means can be secured.

According to the sixteenth aspect of the invention, the gain of theintegrated circuit main body due to a reduction in junction capacity ofMOSFET can be made lower than when the gate voltage of the monitoringMOSFET of the substrate voltage regulating means is constant. Besides,variations in threshold value of individual MOSFETs within theintegrated circuit main body can be suppressed even when the temperatureis changed.

According to the seventeenth aspect of the invention, the thresholdvalue regulated by a circuit generating a constant threshold value (Vth)can be set to be higher at the time of a clock low frequency than at thetime of a high frequency for the integrated circuit main body. Thus,MOSFET device leakage is reduced during the use at a low frequency.

According to the eighteenth aspect of the invention, voltage variationbetween the source and substrate of the n-type MOSFET is reduced, thusenabling high-precision application of a substrate voltage.

According to the nineteenth aspect of the invention, voltage variationbetween the source and substrate of the n-type MOSFET is reduced, thusenabling high-precision application of a substrate voltage.

According to the twentieth aspect of the invention, voltage variationbetween the source and substrate of the n-type MOSFET is reduced, thusenabling higher-precision application of a substrate voltage.

According to the twenty-first aspect of the invention, the integratedcircuit main body comprises a feedback buffer and the substrate voltageof the MOSFET of the feedback buffer is set by the substrate voltageregulating means. With this configuration, stable operation of thesemiconductor integrated circuit apparatus is allowed even when thefeedback buffer is driven on a low voltage. Moreover, the leakagecurrent is reduced.

According to the twenty-second aspect of the invention, the integratedcircuit main body comprises a memory circuit and the substrate voltageof the MOSFET of the memory circuit is set by the substrate voltageregulating means. It is thus possible to control the source-substratevoltage value of the MOSFET in the memory circuit so that the draincurrent for an arbitrary gate voltage value in a subthreshold regionwill be free from temperature dependence and process variationdependence, thereby preventing corruption of memory data by asubthreshold leakage.

According to the twenty-third aspect of the invention, the integratedcircuit main body comprises an SRAM and the substrate voltage of theMOSFET of the SRAM is set by the substrate voltage regulating means. Itis thus possible to reduce the temperature dependence of the noisemargin at low voltages. This allows operation of the semiconductorintegrated circuit apparatus at a low voltage thereby reducing the powerconsumption of the SRAM.

According to the twenty-fourth aspect of the invention, the integratedcircuit main body comprises a circuit of the timing borrow system andthe substrate voltage of the MOSFET of the circuit of the timing borrowsystem is set by the substrate voltage regulating means. It is thuspossible to reduce the temperature dependence and process variationdependence of a circuit of the tinting borrow system, since the staticnoise margin of the circuit of the timing borrow system is determined bythe threshold value of the MOSFET. It is also possible to reduce theleakage current in the circuit of the timing borrow system.

According to the twenty-fifth aspect of the invention, the integratedcircuit main body comprises a differential operational amplifier and thesubstrate voltage of the MOSFET of the differential operationalamplifier is set by the substrate voltage regulating means. It is thuspossible to reduce the temperature dependence and process variationdependence of the lower limit voltage in the output range of thedifferential operational amplifier.

According to the twenty-sixth aspect of the invention, the integratedcircuit main body comprises a voltage-controlled oscillator and thesubstrate voltage of the MOSFET of the voltage-controlled oscillator isset by the substrate voltage regulating means. It is thus possible toreduce the temperature dependence and process variation dependence ofthe frequency response with respect to the input voltage of thevoltage-controlled oscillator.

According to the twenty-seventh aspect of the invention, the integratedcircuit main body comprises a CMOS logic circuit and the substratevoltage of the MOSFET of the CMOS logic circuit is set by the substratevoltage regulating means.

It is thus possible to reduce the temperature dependence and processvariation dependence of a delay in the CMOS logic circuit.

According to the twenty-eighth aspect of the invention, the integratedcircuit main body comprises a current-controlled oscillator and thesubstrate voltage of the MOSFET of the current-controlled oscillator isset by the substrate voltage regulating means. It is thus possible tokeep constant the delay value of the current-controlled oscillator andreduce the temperature dependence and process variation dependence ofthe oscillating frequency.

1-2. (canceled)
 29. A substrate voltage regulating circuit forregulating the substrate voltage of a semiconductor integrated circuitcomprising: a monitoring circuit including a first monitoring MOSFET;and a frequency-voltage conversion circuit to which a clock supplied tosaid semiconductor integrated circuit is inputted, wherein a frequencyof said clock is converted into an output voltage by saidfrequency-voltage conversion circuit, said output voltage is applied tosaid monitoring circuit, a source potential of said first monitoringMOSFET is changed based on said output voltage, and the substratevoltage of said semiconductor integrated circuit is controlled based ona drain potential of said first monitoring MOSFET.
 30. The substratevoltage regulating circuit of claim 29, further comprising: a firstconstant current source for supplying a constant current to said firstmonitoring MOSFET, and a first comparison unit for comparing the sourcepotential of said first monitoring MOSFET with a reference potential,and feeding back a comparison result to the substrate voltage of saidsemiconductor integrated circuit.
 31. The substrate voltage regulatingcircuit according to claim 30, wherein said reference potential is asupply potential of said semiconductor integrated circuit.
 32. Thesubstrate voltage regulating circuit according to claim 31, furthercomprising: a second monitoring MOSFET; a second constant current sourcefor supplying a constant current to said second monitoring MOSFET, and acomparison unit for comparing a drain potential of said secondmonitoring MOSFET with the reference potential, and feeding back acomparison result to a second substrate voltage of said semiconductorintegrated circuit.
 33. A substrate voltage regulating circuit forregulating the substrate voltage of a semiconductor integrated circuitcomprising: a monitoring circuit including at least one monitoringMOSFET; and a frequency-voltage conversion circuit to which a clocksupplied to said semiconductor integrated circuit is inputted, wherein afrequency of said clock is converted into an output voltage by saidfrequency-voltage conversion circuit, said output voltage is applied tosaid monitoring circuit, a drain potential of said monitoring MOSFET ischanged based on said output voltage, and the substrate voltage of saidsemiconductor integrated circuit is controlled based on the drainpotential of said monitoring MOSFET.
 34. A substrate voltage regulatingcircuit for regulating the substrate voltage of a semiconductorintegrated circuit comprising: a monitoring circuit including at leastone monitoring MOSFET; and a voltage conversion circuit to which asignal generated in response to a clock supplied to said semiconductorintegrated circuit is inputted, wherein an output voltage is generatedbased on said signal by the voltage conversion circuit, said outputvoltage is applied to said monitoring circuit, a source potential ofsaid monitoring MOSFET is changed based on said output voltage, and thesubstrate voltage of said semiconductor integrated circuit is controlledbased on the source potential of said monitoring MOSFET.
 35. A substratevoltage regulating circuit for regulating the substrate voltage of asemiconductor integrated circuit comprising: a monitoring circuitincluding a first monitoring MOSFET, and a voltage conversion circuit towhich a signal generated in response to a clock supplied to saidsemiconductor integrated circuit is inputted, wherein an output voltageis generated based on said signal by the voltage conversion circuit,said output voltage is applied to said monitoring circuit, a sourcepotential of said first monitoring MOSFET is changed based on saidoutput voltage, and the substrate voltage of said semiconductorintegrated circuit is controlled based on a drain potential of saidfirst monitoring MOSFET.